Researchers find the cause of a rare and fatal disease that bluishes the lips and skin of babies

CINCINNATI – Scientists have used a gene editing method called CRISPR / Cas9 to generate mice that faithfully mimic a fatal respiratory disorder in the newborn, which blushes his lips and skin. The new laboratory model has allowed researchers to identify the cause of the disease and develop a potential and desperately needed treatment based on nanoparticles.

Alveolar capillary dysplasia, usually poorly treated, with misalignment of the pulmonary veins (ACDMPV) usually strikes infants less than a month after birth, according to researchers at the Cincinnati Children's Hospital Medical Center, which publish the results American Journal of Respiratory and Critical Care Medicine. The disease deprives the pulmonary system of oxygen after the blood vessels of the lung do not form properly during the development of the organ. The absence of tiny blood vessels called alveolar capillaries causes hypoxia, inflammation and death.

"There is no effective treatment other than a lung transplant, so it's urgent to find new treatments," said Vlad Kalinichenko, MD, PhD, of the Lung Regenerative Medicine Center. the Cincinnati Children's Perinatal Institute, and principal investigator. "We have identified a nanoparticle-based therapeutic strategy to increase the number of alveolar capillaries and help preserve the respiratory function of at least one subgroup of babies with this congenital lung disease."

The disease has long been linked to mutations in the FOXF1 gene, an important regulator of embryonic lung development. According to the researchers, the mystery that remains to be seen until this study concerns the precise microbiological processes that feed the ACDMPV.

In collaboration with the team of Dr. Pawel Stankiewicz of Baylor College of Medicine in Houston, Kalinichenko Laboratory analyzed genetic information from human ACDMPV cases to generate the first animal model of ACDMPV presenting a clinical interest. They used CRISPR / Cas9 to recreate mutations of human FOXF1 in mice. CRISPR-Cas9 allows accurate editing of genes using an enzyme to cut specific sections of a DNA sequence and attaching the free ends to a desired point to alter the genetic makeup of the DNA. ;a cell.

Having clinically accurate mouse models of the disease, ACDMPV, allowed the authors to overcome a long-standing obstacle to understanding the development of the disease.

The work also supported extensive bioinformatic analyzes of clinical and laboratory data from biological tests. This includes a technique called ChIP-Seq (which analyzes protein-DNA interactions) and whole exome sequencing (which reveals the arrangement of all regions of the genes encoding proteins).

By studying FOXF1 gene-related protein-DNA interactions in lung cells, the authors of the study found a point mutation involving FOXF1 at the binding site of S52F DNA to the FOXF1 nuclear protein. The mutation blocked molecular signaling to several downstream target genes involved in the formation of pulmonary blood vessels.

They also discovered that the mutant S52F FOXF1 protein did not interact with a protein called STAT3. The link is essential to stimulate the development of blood vessels in the neonatal lung. This led to STAT3 deficiency in lung development and poor formation of the pulmonary circulatory system.

The researchers also found a STAT3 deficiency in samples from patients treated with ACDMPV who had specific point mutations in the FOXF1 gene. The authors hypothesized that treatment of newborn mice with STAT3 would stimulate the development of blood vessels in the lungs, but they had to figure out how to get the protein to the lungs.

Researchers turned to nanoparticle technology to deliver a mini STAT3 gene to the lungs of newborn mice. They created a new formulation for what is known as polyethylene imine nanoparticles (PEI).

The gelatin-type PEI nanoparticles can carry therapeutic genetic material into different parts of the body by administering them intravenously to patients. Different PEI nanoparticle formulations are currently being tested in adult cancer clinical trials in other institutions, according to the study's authors.

Therapeutic administration of STAT3 DNA to newborn mice with the S52F FOXF1 mutation restored the ability of endothelial cells to form pulmonary blood vessels. This stimulates the growth of blood vessels in animals and the formation of air sacs called alveolar.

"If the efficacy of PEI nanoparticles is confirmed in ongoing clinical trials in adult cancer, PEI could be considered for STAT3 gene therapy in infants with ACDMPV," said Kalinichenko. . "Considering that ACDMPV is a rare disease, a multicenter clinical trial would be needed to evaluate the efficacy of STAT3 gene therapy in newborns and infants of ACDMPV."

The first author of the study is Arun Pradhan, PhD, a researcher who works in the Kalinichenko laboratory.

Funding for this study was provided by the National Institutes of Health (HL84151, HL141174, HL123490, HL137203, HL132849 and grants from the National Organization for Rare Disorders).

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